She does seem as if she is celebrating. For me, I wish there was a bit more of her (not having her hand cut off) or something in the background to tell me what she is celebrating...did she win a race? I find the blue gum in her mouth a bit...distracting, but I like her rosy cheeks and smile.
Great expression and angle, would be stronger imho if the left hand wasn't cut out, though it does look ok as it's not cropped right at the wrist. The bright colors add impact as well.